1. Field of the Invention
The present invention relates generally to a television receiver, and is directed more particularly to a television receiver having a mode changing device to changeably supply a received television signal or an external video signal to its cathode ray tube.
2. Description of the Prior Art
A prior art television receiver of this kind is shown in FIG. 1. In FIG. 1, a broadcast television signal is received by an antenna 1, then selected by a tuner 2 and a channel selector 3, amplified by an intermediate frequency amplifier 4, detected by a video detector 5, and connected to a change-over terminal a of a change-over switch 8, and to an external output terminal t.sub.out. When the switch 8 is contacted with the terminal a, the television signal from the video detector 5 is supplied through a video amplifier 6 to a cathode ray tube 7.
The switch 8 is used to select between the television signal fed to the terminal a and an external signal fed to a terminal b. A signal from a video tape recorder, television camera or the like is generally used as the external signal. In the prior art example shown in FIG. 1, a video tape recorder 9 is used, and the terminal b is connected through an external input terminal t.sub.in to the output terminal of video tape recorder 9. The external output terminal t.sub.out is connected to the input terminal of video tape recorder 9.
The tuner 2 is of a voltage controlled type and has an inner reactance element (for example, a variable capacitance diode) 20, so that when a voltage applied across the both ends thereof is varied, a channel of a predetermined frequency can be selected. The channel selector 3 serves to apply a voltage in accordance with a channel to be selected to the element 20 of tuner 2. To this end, the channel selector 3 includes channel selecting switches 301, 302, . . . , switching transistors 311, 312, . . . , channel selecting voltage preset variable resistors 321, 322, . . . , channel selecting display neon lamps 331, 332, . . . , diodes 341, 342, . . . , and a channel selecting block 30 including a pulse generator 31, a counter 32 and a decoder 33.
FIG. 2 shows a part of the control portion of the television receiver shown in FIG. 1. The control portion is located, for example, on one side of the front portion of the television receiver. Usually, the dotted line block 200 of the control portion shown in FIG. 2 is covered with a lid (not shown). Channel selecting buttons 201, 202, . . . are push buttons of the self-return type. Thus, only when the buttons 201, 202, . . . are pushed down manually are, the switches 301, 302, . . . which correspond to buttons 201, 202, . . . , respectively, shown in FIG. 1, closed or made ON. These buttons 201, 202, . . . can be formed as contact electrodes of touch switches. At channel display portions 231, 232, . . . there are provided figures, letters or the like for displaying the selected channel by lighting one of neon lamps 331, 332, . . . shown in FIG. 1. These operating buttons 201, 202, . . . and channel display portions 231, 232, and so on . . . are exposed for direct viewing. However on the portion 200, which is covered by the lid, there are located buttons which are used less frequently. That is, preset knobs 221, 222, . . . , which correspond to the variable resistors 321, 322, . . . for presetting the selecting voltage, and so on are located on the covered portion 200 because if they are preset at predetermined channels, almost no adjustment for them is necessary. A slide switch 28 for selecting the television signal receiving mode or the video tape recorder reproducing mode is also located on the covered portion 200.
On some prior art television receivers controls, which are used less frequently, are located either on the side panel or back panel of the receiver, and usually apart from the channel selecting buttons 201, 202, . . . , mainly to enhance the appearance of the television receiver.
With the above prior art television receivers, if the mode changing switch 28 is switched to the video tape recorder side, no picture will appear on the screen of the television receiver even though the power switch is closed and any one of the channel selecting buttons 201, 202, . . . is pushed down. In this case, if the slide switch 28 is covered with the lid or the like as in the prior art, a user may not understand and conclude that the television receiver is out of order.
Further, with a television receiver of the prior art the mode changing operation is different from the channel changing operating, the operation efficiency is poorer and it is troublesome to transfer from the video tape recorder output to a desired television channel.